A group of New York moms has filed suit against the makers of a “99.9-percent accurate” baby-gender test, claiming the results they got were 100 percent wrong.

The product was advertised as “infallibly accurate in foretelling the gender of a healthy baby,” and its Web site said the “prediction of your baby’s gender is unmistakably correct or we will double your money back.”

The Baby Gender Mentor is touted as allowing women as little as five weeks pregnant to tell if they’re expecting a boy or a girl, the suit says.

That’s nine to 13 weeks sooner than parents normally find out from a sonogram or amniocentesis and typically the cutoff point for abortions — although no one suggested in the court papers that was the reason they took the test.

In papers filed in Manhattan Supreme Court, six New York women claim they were given incorrect results from the $275 test, and claim the company, Acu-Gen Biolab, Inc., made them jump through hoops to get their refunds — or, in some cases, simply refused to pay.

“They’re just hoping these people will go away,” said the moms’ lawyer, Barry Gainey.

He said in a pending federal class-action lawsuit against the company that officials admitted that 10 to 20 percent of their customers have asked for refunds based on incorrect results.

“That doesn’t sound like 99.9 percent accurate to me,” Gainey said.

Keven Duffy, 41, said she took the test three years ago “on the sly” in hopes of being able to surprise her husband with the news that they were going to have a son. The couple already had a daughter, and was hoping for a boy for “family balancing.”

She double-checked the results with the company, and “they said for sure it’s a boy” — so she told her hubby the good news. Several weeks later, a sonogram revealed they were having a girl.

“I feel they’re just tricksters,” she said

The company allegedly told her it wouldn’t refund her money unless there was a live birth and she sent them an original birth certificate — and then stopped returning her calls. The flip-flop “caused stress” in her marriage, Duffy said, and she and her husband have since divorced.